Artificial functional spinal unit system and method for use

ABSTRACT

A stabilization system for a human spine is provided comprising at least one dynamic interbody device and at least one dynamic posterior stabilization system. In some embodiments the stabilization system comprises a pair of dynamic interbody devices and a pair of dynamic posterior stabilization systems. In some embodiments, a bridge may couple a dynamic interbody device to a dynamic posterior stabilization system. In some embodiments, an elongated member of the dynamic posterior stabilization system may be curved.

PRIORITY CLAIM

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/634,950 to Gordon et al., filed on Aug. 5, 2003 and entitled“Artificial Functional Spinal Unit Assemblies”, which is incorporatedherein by reference.

BACKGROUND

1. Field of the Invention

Embodiments of the invention generally relate to functional spinalimplant assemblies for insertion into an intervertebral space betweenadjacent vertebrae of a human spine, and reconstruction of the posteriorelements to provide stability, flexibility, and proper biomechanicalmotion. More specifically, embodiments of the invention relate toartificial functional spinal units including an artificialintervertebral implant that can be inserted via a posterior surgicalapproach and used in conjunction with one or more dynamic posteriorstabilization systems to approach an anatomically correct range ofmotion and segmental stiffness. Embodiments of the invention may also beinserted via an anterior surgical approach.

2. Description of Related Art

The human spine is a complex mechanical structure including alternatingbony vertebrae and fibrocartilaginous discs that are connected by strongligaments and supported by musculature that extends from the skull tothe pelvis and provides axial support to the body. The intervertebraldiscs provide mechanical cushion between adjacent vertebral segments ofthe spinal column and generally include two basic components: thenucleus pulposus and the annulus fibrosis. The intervertebral discs arepositioned between two vertebral end plates. The annulus fibrosis formsthe perimeter of the disc and is a tough outer ring that binds adjacentvertebrae together. The end plates are made of thin cartilage overlyinga thin layer of hard cortical bone that attaches to the spongy,cancellous bone of a vertebra. The vertebrae generally include avertebral foramen bounded by the anterior vertebral body and the neuralarch, which consists of two pedicles that are united posteriorly by thelaminae. The spinous and transverse processes protrude from the neuralarch. The superior and inferior articular facets lie at the root of thetransverse process.

The human spine is a highly flexible structure capable of a high degreeof curvature and twist in nearly every direction. However, genetic ordevelopmental irregularities, trauma, chronic stress, and degenerativewear can result in spinal pathologies for which surgical interventionmay be necessary. In cases of deterioration, disease, or injury, anintervertebral disc, or a portion of the intervertebral disc may beremoved from the human spine during a discectomy.

After some discectomies, an intervertebral device may be placed in thedisc space to fuse or promote fusion of the adjacent vertebrae. Duringsome procedures, fusion may be combined with posterior fixation toaddress intervertebral disc and/or facet problems. The fusion procedure(e.g., posterior lumbar interbody fusion) and the posterior fixationprocedure may be performed using a posterior approach. The posteriorfixation may inhibit motion and promote bone healing. Fusing twovertebrae together may result in some loss of motion. Fusing twovertebrae together may also result in the placement of additional stresson one or more adjacent functional spinal units. The additional stressmay cause deterioration of an adjacent functional spinal unit that mayresult in the need for an additional surgical procedure or procedures.

After some discectomies, an intervertebral dynamic device may be placedin the disc space. The dynamic device may allow for movement of thevertebrae coupled to the disc dynamic device relative to each other.U.S. Pat. No. 4,863,477 to Monson, which is incorporated herein byreference, discloses a resilient dynamic device intended to replace theresilience of a natural human spinal disc. U.S. Pat. No. 5,192,326 toBao et al., which is incorporated herein by reference, describes aprosthetic nucleus for replacing just the nucleus portion of a humanspinal disc. U.S. Patent Application Publication No. 2005/0021144 toMalberg et al., which is incorporated herein by reference, describes anexpandable spinal implant. Allowing for movement of the vertebraecoupled to the disc prosthesis may promote the distribution of stressthat reduces or eliminates the deterioration of adjacent functionalspinal units.

An intervertebral device may be positioned between vertebrae using aposterior approach, an anterior approach, a lateral approach, or othertype of approach. A challenge of positioning a device between adjacentvertebrae using a posterior approach is that a device large enough tocontact the end plates and slightly expand the space must be insertedthrough a limited space. This challenge is often further heightened bythe presence of posterior osteophytes, which may cause “fish mouthing”of the posterior vertebral end plates and result in very limited accessto the disc. A further challenge in degenerative disc spaces is thetendency of the disc space to assume a lenticular shape, which mayrequire a larger implant than can be easily introduced without causingtrauma to adjacent nerve roots. The size of rigid devices that maysafely be introduced into the disc space is thereby limited. During somespinal fusion procedures using a posterior approach, two implants areinserted between the vertebrae. During some posterior procedures, one orboth facet joints between the vertebrae may be removed to provideadditional room for the insertion of a fusion device.

The anterior approach poses significant challenges as well. Though thesurgeon may gain very wide access to the interbody space from theanterior approach, this approach has its own set of complications. Theretroperitoneal approach usually requires the assistance of a surgeonskilled in dealing with the visceral contents and the great vessels, andthe spine surgeon has extremely limited access to the nerve roots.Complications of the anterior approach that are approach specificinclude retrograde ejaculation, ureteral injury, and great vesselinjury. Injury to the great vessels may result in massive blood loss,postoperative venous stasis, limb loss, or death. The anterior approachis more difficult in patients with significant obesity and may bevirtually impossible in the face of previous retroperitoneal surgery.

Furthermore, disc degeneration is often coupled with facet degeneration.Facet degeneration is addressed using a posterior approach. Thus asecond surgical approach may be required if the disc degeneration istreated using an anterior approach. The need to address facetdegeneration has led to the development of facet replacement devices.Some facet replacement devices are shown in U.S. Pat. No. 6,419,703 toFallin et al.; U.S. Pat. No. 6,902,580 to Fallin et al.; U.S. Pat. No.6,610,091 to Reiley; U.S. Pat. No. 6,811,567 to Reiley; and U.S. Pat.No. 6,974,478 to Reiley et al, each of which is incorporated herein byreference. The facet replacement devices may be used in conjunction withanterior disc replacement devices, but the facet replacement devices arenot designed to provide a common center of rotation with the anteriordisc replacement devices. The use of an anterior disc replacement devicethat has a fixed center of rotation contrary to the fixed center ofrotation of the facet replacement device may restrict or diminish motionand be counterproductive to the intent of the operation.

Despite the difficulties of the anterior approach, the anterior approachdoes allow for the wide exposure needed to place a large device. Inaccessing the spine anteriorly, one of the major structural ligaments,the anterior longitudinal ligament, must be completely divided. A largeamount of anterior annulus must also be removed along with the entirenucleus. Once these structures have been resected, the vertebral bodiesmay need to be over distracted to place the device within the disc spaceand restore disc space height. Failure to adequately tension theposterior annulus and ligaments increases the risk of device failureand/or migration. Yet in the process of placing these devices, theligaments are overstretched while the devices are forced into the discspace under tension. Over distraction can damage the ligaments and thenerve roots. The anterior disc replacement devices currently availableor in clinical trials may be too large to be placed posteriorly, and mayrequire over distraction during insertion to allow the ligaments to holdthem in position.

During some spinal stabilization procedures a posterior fixation systemmay be coupled to the spine. During some procedures, posterior fixationsystems may be coupled to each side of the spine. The posterior fixationsystems may include elongated members that are coupled to vertebrae byfasteners (e.g., hooks and screws). In some embodiments, one or moretransverse connectors may be connected to the posterior fixation systemsto join and stabilize the posterior fixation systems.

During some spinal stabilization procedures, dynamic posteriorstabilization systems may be used. U.S. Patent Application Nos.2005/0182409 to Callahan et al.; 2005/0245930 to Timm et al.; and2006/0009768 to Ritland, each of which is incorporated herein byreference, disclose dynamic posterior stabilization systems.

SUMMARY

One or more dynamic interbody devices for a spine may be inserted in adisc space between vertebrae. In addition to one or more dynamicinterbody devices, at least one dynamic posterior stabilization systemsmay be coupled to the vertebrae. In an embodiment, a stabilizationsystem for a human spine includes at least one dynamic interbody deviceconfigured to be positioned in a disc space between a first vertebra anda second vertebra; and

at least one dynamic posterior stabilization system configured to becoupled to the first vertebra and the second vertebra. At least onedynamic posterior stabilization system includes a first bone fastenerconfigured to be coupled to the first vertebra, a second bone fastenerconfigured to be coupled to the second vertebra, and an elongated memberconfigured to be coupled to the first bone fastener and the second bonefastener. The elongated member is coupled to the second bone fastenersuch that the second bone fastener can move relative to the elongatedmember to accommodate movement of vertebrae coupled to the first bonefastener and the second bone fastener. At least a portion of theelongated member is curved.

In some embodiments, at least one dynamic interbody device includes acenter of rotation that accommodates flexion of vertebra coupled to thedynamic interbody device. A center of curvature of the curved portion ofthe elongated member aligns or substantially aligns with the center ofrotation of the dynamic interbody device when the dynamic interbodydevice and the dynamic posterior stabilization system are coupled tovertebrae.

In some embodiments, a stabilization system for a human spine includesat least one dynamic interbody device configured to be positioned in adisc space between a first vertebra and a second vertebra and at leastone dynamic posterior stabilization system configured to be coupled tothe first vertebra and the second vertebra. At least one dynamicposterior stabilization system includes a first bone fastener configuredto be coupled to the first vertebra, a second bone fastener configuredto be coupled to the second vertebra, and an elongated member configuredto be coupled to the first bone fastener and the second bone fastenerwhen the first bone fastener and second bone fastener are coupled to thefirst vertebra and the second vertebra. At least a portion of theelongated member is curved. When the elongated member is coupled to thefirst bone fastener, longitudinal movement of the first bone fastenerrelative to the elongated member is inhibited. When the elongated memberis coupled to the second bone fastener, the second bone fastener isallowed to move longitudinally along a portion of the elongated memberto accommodate flexion of the second vertebra relative to the firstvertebra.

In some embodiments, a method of stabilizing a portion of the humanspine includes coupling at least one dynamic interbody device to a firstvertebra and a second vertebra, securing a first bone fastener to thefirst vertebra, securing a second bone fastener to the second vertebra,coupling an elongated member to the first bone fastener to inhibitmovement of the first bone fastener longitudinally with respect to theelongated member, and coupling the elongated member to the second bonefastener to allow longitudinal movement of the elongated member withrespect to the second bone fastener. At least a portion of the elongatedmember is curved.

In some embodiments, the method may also include securing a third bonefastener to a third vertebra, coupling a second elongated member to thesecond bone fastener to inhibit movement of the second bone fastenerlongitudinally with respect to the second elongated member, and couplingthe elongated member to the third bone fastener to allow longitudinalmovement of the third elongated member with respect to the third bonefastener. The second elongated member forms a portion of a multi-leveldynamic posterior stabilization system.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will become apparent to thoseskilled in the art with the benefit of the following detaileddescription and upon reference to the accompanying drawings in which:

FIG. 1 depicts a schematic view of a portion of an embodiment of aspinal stabilization system.

FIG. 2 depicts a perspective view of an embodiment of a dynamicinterbody device.

FIG. 3 depicts a perspective view of a first member of the dynamicinterbody device depicted in FIG. 2.

FIG. 4 depicts a side view of an embodiment of a separate componentbridge.

FIG. 5 depicts a perspective view of a second member of the dynamicinterbody device depicted in FIG. 2.

FIG. 6 depicts a perspective view of a third member of the dynamicinterbody device depicted in FIG. 2.

FIG. 7 depicts a cross-sectional view of a third member of a dynamicinterbody device.

FIG. 8 depicts a perspective view of embodiments of dynamic interbodydevices.

FIG. 9 depicts a perspective view of an embodiment of a posteriorstabilization system.

FIG. 10 depicts a perspective view of an embodiment of a closure member.

FIG. 11 depicts a side view of an embodiment of an elongated member.

FIG. 12 depicts a plot of applied moment versus rotation.

FIG. 13 depicts the components of an embodiment of a first bone fastenerof a dynamic posterior stabilization system.

FIG. 14 depicts a top view of an embodiment of a fastener and collarcombination for a bone fastener.

FIG. 15 depicts the components of an embodiment of a second bonefastener of a dynamic posterior stabilization system.

FIG. 16 depicts an embodiment of a dynamic posterior stabilizationsystem with a laterally positioned elongated member.

FIG. 17 depicts a front view representation of the second bone fastenerdepicted in is FIG. 16.

FIG. 18 depicts an embodiment of a multi-level dynamic posteriorstabilization system.

FIG. 19 depicts an embodiment of a dynamic posterior stabilizationsystem.

FIG. 20 depicts top view representation of an embodiment of a dynamicposterior stabilization system.

FIG. 21 depicts a front view representation of a portion of anembodiment of a second bone fastener of a dynamic posteriorstabilization system.

FIG. 22 depicts a side view representation of a portion of an embodimentof a dynamic posterior stabilization system with a bridge, wherein aportion of the first bone fastener is depicted in cutaway to emphasizethe interior of the first bone fastener.

FIG. 23 depicts a perspective view of an embodiment of a dynamicposterior stabilization system.

FIG. 24 depicts a perspective view of the elongated member of thedynamic posterior stabilization system depicted in FIG. 23.

FIG. 25 depicts the first bone fastener of the dynamic posteriorstabilization system after insertion of the elongated member.

FIG. 26 depicts a representation of a dynamic interbody device and aposterior stabilization system coupled to vertebrae.

FIG. 27 depicts a representation of a transverse connector that couplesa first dynamic posterior stabilization system to a second dynamicposterior stabilization system.

FIG. 28 depicts a representation of pins placed in vertebrae to bestabilized.

FIG. 29 depicts a representation of a distractor plug and a keel cutterduring a spinal stabilization procedure.

FIG. 30 depicts a representation of dynamic interbody devices insertedin a disc space between vertebrae.

FIG. 31 depicts a representation of an embodiment of a dynamic interbodydevice and an embodiment of a dynamic posterior stabilization system ofa spinal stabilization system.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Thedrawings may not be to scale. It should be understood, however, that thedrawings and detailed description thereto are not intended to limit theinvention to the particular form disclosed, but to the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

DETAILED DESCRIPTION

A “functional spinal unit” generally refers to a motion segment of aspine. The functional spinal unit may include two vertebrae, anintervertebral disc between the vertebrae, and the two facet jointsbetween the vertebrae. An “artificial functional spinal unit” refers toa functional spinal unit where one or more of the components of thefunctional spinal unit are replaced by implants or devices that permitat least some motion of the spine. At least a portion of theintervertebral disc and/or one or both of the facet joints may bereplaced by implants or devices during a spinal stabilization procedure.

As used herein, “coupled” includes a direct or indirect joining ortouching unless expressly stated otherwise. For example, a first memberis coupled to a second member if the first member contacts the secondmember, or if a third member is positioned between the first member andthe second member.

A “dynamic interbody device” generally refers to an artificialintervertebral implant that allows for flexion/extension, lateralbending and/or axial rotation of vertebrae coupled to the device. Thedynamic interbody device may replace a portion or all of anintervertebral disc. In some embodiments, a pair of dynamic interbodyimplants are installed during a spinal stabilization procedure. In someembodiments, a dynamic interbody device is installed using a posteriorapproach. In other embodiments, a dynamic interbody device may beinstalled using an anterior approach or other type of approach. In someembodiments, one or more dynamic interbody devices are placed in a discspace between vertebrae, and at least one posterior stabilization systemis coupled to the vertebrae. In some embodiments, one or more dynamicinterbody devices are placed in the disc space without coupling aposterior stabilization system to the vertebrae.

Dynamic interbody devices may have surfaces that contact vertebrae. Insome embodiments, a surface of the dynamic interbody device thatcontacts a vertebra may include one or more keels, protrusions, and/orosteoconductive/osteoinductive layers or coatings. A keel of the dynamicinterbody device may be positioned in a groove formed in a vertebra. Thegroove may be formed in the vertebra so that the dynamic interbodydevice will be positioned at a desired location when inserted into thepatient. Protrusions of the dynamic interbody device may penetrate anendplate of the vertebra to secure the dynamic interbody device to thevertebra. An osteoconductive/osteoinductive layer may promote bonegrowth that secures the dynamic interbody device to the vertebra. Theosteoconductive/osteoinductive layer may include, but is not limited toa scaffold, a roughened surface, a surface treated with a titaniumplasma spray, bone morphogenic proteins, and/or hydroxyapatite. Aroughened surface may be formed by chemical etching, by surfaceabrading, by shot peening, by an electrical discharge process, and/or byembedding particles in the surface.

A dynamic interbody device may include one or more angled surfaces sothat the dynamic interbody device provides the patient with a desiredamount of lordosis. Dynamic interbody devices that provide differentamounts of lordosis may be provided in an instrument kit supplied for aspinal stabilization procedure. For example, the instrument kit for aspinal stabilization procedure may include pairs of dynamic interbodydevices that establish 0°, 3°, 6°, 9°, 12° or 15° of lordosis. Pairs ofdynamic interbody devices that provide other amounts of lordosis may beprovided. The amount of lordosis provided by a dynamic interbody devicemay be printed or etched on a visible surface of the dynamic interbodydevice. Other information may also be printed or etched on the visiblesurface of the dynamic interbody device. Such information may includedimension information (e.g., length, width, and/or height) and whetherthe dynamic interbody device is to be installed on the left side of thepatient or the right side of the patient.

In some embodiments, one or more dynamic interbody devices are installedin a disc space formed in the lumbar region of the spine during a spinalstabilization procedure. The shape and/or size of a dynamic interbodydevice may depend on a number of factors including surgical approachemployed for insertion, intended position in the spine (e.g., cervicalor lumbar), and patient anatomy. A dynamic interbody device for thelumbar spine may have a height that is less than about 22 mm. Severalsizes of interbody devices may be provided in the instrument kit for thespinal stabilization procedure. In an embodiment, dynamic interbodydevices having heights of 6 mm, 8 mm, 10 mm, 12, mm, 14 mm, 16 mm, 18mm, and 20 mm are provided in the instrument kit for the spinalstabilization procedure. The dynamic interbody devices may includeindicia indicating the height of the spinal stabilization devices.

In some embodiments, a single dynamic interbody device may be positionedin a disc space between vertebrae. The dynamic interbody device may beinstalled using an anterior approach, a posterior approach, or adifferent type of approach. In some embodiments, the height of thedynamic interbody device may be adjustable during the installationprocedure. U.S. Patent Application Publication No. 2005/0278026 toGordon et al., which is incorporated herein by reference, describesexpandable dynamic spinal implants. In some embodiments, insertioninstruments may change the separation distance between endplates of thedynamic interbody device. One or more shims may be coupled to thedynamic interbody device to maintain the selected separation distance.

In some embodiments, a pair of dynamic interbody devices may beinstalled between a pair of vertebrae to establish a stabilizationsystem. In some embodiments, the dynamic interbody device is a bimodaldevice. Bimodal refers to a device that has two separate curved surfacesto accommodate flexion/extension, lateral bending and/or axial rotation.

FIG. 1 depicts an anterior view of an embodiment of a portion of astabilization system positioned between vertebrae. Dynamic interbodydevice 50′ may be positioned on a first side of the patient. Dynamicinterbody device 50″ may be positioned on the contralateral side of thepatient. Dynamic interbody device 50′ may be the mirror image of dynamicinterbody device 50″. Dynamic interbody devices 50′, 50″ may be bimodaldevices. Dynamic interbody devices 50′, 50″ may provide sufficientcontact area against end plates of vertebrae 52, 54 to support thespinal column and inhibit subsidence of the vertebrae.

Each dynamic interbody device 50′, 50″ of the pair of dynamic interbodydevices may have a width that is significantly less than the width of asingle dynamic interbody device that can be installed in the disc spacebetween first vertebra 52 and second vertebra 54. Using two interbodydevices 50′, 50″ may limit the amount of bone and tissue removal neededfor insertion using a posterior approach. Each of the dynamic interbodydevices may have a width that is less than 17 mm. In some embodiments,the dynamic interbody devices may be provided in pairs having small,medium or large widths. The instrument kit for the spinal stabilizationprocedure may include one or more sizes of dynamic interbody devices. Inan embodiment, the instrument kit includes dynamic interbody devicepairs having medium and large widths.

As used herein a “dynamic posterior stabilization system” generallyrefers to an apparatus used to replace or supplement a facet joint whileallowing for both dynamic resistance and at least some motion of thefirst vertebra to be stabilized relative to the second vertebra to bestabilized. The first vertebra and the second vertebra may be vertebraeof a functional spinal unit. In some embodiments, bone fasteners of thedynamic posterior stabilization system are secured to the first vertebraand the second vertebra. In some embodiments, a bone fastener of thedynamic posterior stabilization system may be coupled to a vertebraadjacent to the vertebrae of the functional spinal unit beingstabilized. The bone fasteners may be coupled to lamina, pedicles,and/or vertebral bodies of the vertebrae. In some embodiments, dynamicposterior stabilization systems may be positioned in three or morevertebrae to form a multi-level stabilization system.

The dynamic posterior stabilization system may replace or supplement anormal, damaged, deteriorated, defective or removed facet joint. Thedynamic posterior stabilization system may include bone fasteners, anelongated member, and at least one bias member. The bias member mayprovide little initial resistance to movement of a first vertebracoupled to the system relative to a second vertebra coupled to thesystem. Resistance to additional movement of the first vertebra relativeto the second vertebra may increase. The increasing resistance providedby the bias member may mimic the behavior of a normal functional spinalunit. The dynamic posterior stabilization system may stabilize thevertebrae, limit the range of motion of the first vertebra relative tothe second vertebra, and/or share a portion of the load applied to thevertebrae.

The dynamic posterior stabilization systems disclosed herein may allowfor rotational and/or translational motion of an elongated member (e.g.,a rod or plate) relative to one or more bone fasteners. The bonefasteners may include threading, barbs, rings or other protrusions thatsecure the bone fasteners to vertebrae. In some embodiments, the bonefasteners may be cemented or glued to the vertebrae. Bone fasteners mayinclude collars. In some embodiments, a collar of a bone fastener is anintegral portion of the bone fastener. In some embodiments, the collaris a separate component that is coupled to at least one other componentof the bone fastener. The collar of the bone fastener is the portion ofthe bone fastener that couples to an elongated member of the dynamicposterior stabilization system. In some embodiments, the bone fastenersare polyaxial pedicle screws and the collars are the upper portions ofthe polyaxial pedicle screws. In some embodiments, the bone fastenersare bone screws and the collars are plates or other structures that arecoupled to the bone screws.

During installation of dynamic interbody devices of a spinalstabilization system, or during installation of a single dynamicinterbody device, one or both facet joints of the vertebrae may beremoved. A dynamic posterior stabilization system may be installed toreplace a removed facet joint. One or both of the dynamic interbodydevices of the spinal stabilization system, or the single dynamicinterbody device, may be coupled to a dynamic posterior stabilizationsystem. Coupling a dynamic interbody device to the dynamic posteriorstabilization system may inhibit backout of the dynamic interbody devicefrom the disc space. Coupling the dynamic interbody device to thedynamic posterior stabilization system may facilitate operation of thedynamic interbody device with the dynamic posterior stabilizationsystem.

In some embodiments, a dynamic posterior stabilization system may beinstalled without removal of a facet joint. The dynamic posteriorstabilization system may be installed after a discectomy, laminectomy,or other procedure. The dynamic posterior stabilization system maychange the dynamic resistance that is not normal due to degeneration,disease, loss of a portion of the intervertebral disc and/or tissuedamage as a result of the surgery.

A dynamic interbody device and a dynamic posterior stabilization systemmay include one or more biocompatible metals having a non-porous qualityand a smooth finish (e.g., surgical grade stainless steel, titaniumand/or titanium alloys). In some embodiments, a dynamic interbody deviceor dynamic posterior stabilization system may include ceramic and/or oneor more other suitable biocompatible materials, such as biocompatiblepolymers and/or biocompatible metals. Biocompatible polymers mayinclude, but are not limited to, polyetheretherketone resins (“PEEK”),carbon reinforced PEEK, ultra high molecular weight polyethylenes,polyethylenes, polyanhydrides, and alpha polyesters. For example, animplant may be constructed of a combination of biocompatible materialsincluding cobalt chromium alloy, ultra high molecular weightpolyethylene, and polycarbonate-urethane or silicone blend.

In some embodiments, dynamic interbody devices and dynamic posteriorstabilization systems may be made of non-magnetic, radiolucent materialsto allow unrestricted post-operative imaging. Certain material mayinterfere with x-ray and/or magnetic imaging. Magnetic materials mayinterfere with magnetic imaging techniques. Most non-magnetic stainlesssteels and cobalt chrome contain enough iron and/or nickel so that bothmagnetic imaging and x-ray imaging techniques are adversely affected.Other materials, such as titanium and some titanium alloys, aresubstantially iron free. Such materials may be used when magneticimaging techniques are to be used, but such materials are oftenradio-opaque and sub-optimal for x-ray imagining techniques. Manyceramics and polymers are radiolucent and may be used with both magneticimaging techniques and x-ray imaging techniques. The dynamic interbodydevices and/or the dynamic posterior stabilization systems may includecoatings and/or markers that indicate the positions of the devicesand/or systems during operative and/or post-operative imaging.

FIG. 2 depicts a portion of an embodiment of dynamic interbody device50′ that may be positioned on a first side of a patient. Dynamicinterbody device 50′ may include first member 56, second member 58, andthird member 60. Dynamic interbody device 50′ may be positioned in adisc space between two vertebrae. First member 56, second member 58, andthird member 60 may work together to allow for flexion/extension,lateral bending, and/or axial rotation of a vertebra coupled to thefirst member relative to a vertebra coupled to the third member.

FIG. 3 depicts an embodiment of first member 56. First member 56 mayinclude keel 62, slot 64, arms 66, arcuate surface 68 and bridge 70.During an implant insertion procedure, keel 62 may be positioned in achannel formed in a vertebra. Keel 62 may couple first member 56 to thevertebra. The bottom surfaces of first member and keel may beosteoconductive/osteoinductive to promote bone growth that secures thefirst member to the vertebra.

Slot 64 may accommodate a first pin of the second member. In someembodiments, the first member includes a pin that fits in a slot of thesecond member. The first pin may allow the second member to rotaterelative to first member 56 to accommodate axial rotation of thevertebra coupled to the first member relative to the vertebra coupled tothe third member of the dynamic interbody device.

Arms 66 may interact with the second member to limit an amount ofrotation of the second member relative to first member 56. In someembodiments, the position of arms 66 and/or the size of the secondmember allows for up to about 4° of axial rotation (e.g. ±2° of rotationfrom a neutral position). The position of arms 66 and/or the size of thesecond member may be designed to allow for more or less rotation. Insome embodiments, the position of arms 66 and/or the size of the secondmember allows for about ±1.5° of axial rotation from a neutral position.Arms 66 may also inhibit separation of the second member from firstmember 56. Gaps may be present between arms 66 and the second member toallow movement of the second member relative to first member 56 thataccommodates axial rotation and/or lateral bending of vertebrae coupledto the dynamic interbody device.

A first pin of the second member may slide along a length of slot 64 toaccommodate lateral bending of the vertebra coupled to first member 56relative to the vertebra coupled to the third member of the dynamicinterbody device. The curvature of arcuate surface 68 and the length ofslot 64 may allow the dynamic interbody device to accommodate about 10°of lateral bending (e.g. ±5° of lateral bending from a neutralposition). The length of slot 64 and/or the curvature of arcuate surface68 may be designed to allow for more or less lateral bending. In someembodiments, the curvature of arcuate surface 68 and the length of slot64 allows the dynamic interbody device to accommodate about ±3° oflateral bending from a neutral position. In some embodiments, arcuatesurface 68 may be a spherical portion.

Bridge 70 may couple the dynamic interbody device to a dynamic posteriorstabilization system. In some embodiments, bridge 70 is an integral partof first member 56. Bridge 70 may be used to help position keel 62 offirst member 56 in the groove formed in the vertebra. In someembodiments, bridge 70 is attached to the dynamic interbody deviceduring the insertion procedure (e.g., by threading, a slidingconnection, a snap lock connection or other type of connection).Coupling the bridge to the dynamic interbody device and to the dynamicposterior stabilization system connects the two apparatus together sothat one or more centers of rotation that allow for movement of thedynamic interbody device align or substantially align with the curvatureof the elongated member of the dynamic posterior stabilization system sothat the dynamic posterior stabilization system works in conjunctionwith the dynamic interbody device to guide motion of the vertebraecoupled to the dynamic interbody device and to the dynamic posteriorstabilization system.

In some embodiments, two dynamic interbody devices are placed in thedisc space between the vertebrae, and two dynamic posteriorstabilization systems are coupled to the vertebrae. Bridges may couplethe dynamic interbody devices to the dynamic posterior stabilizationsystems. The bridges may fix the position of the dynamic interbodydevices in working relation to each other so that each of the dynamicinterbody devices move during flexion/extension, lateral bending, and/oraxial rotation. The bridges may ensure that the dynamic interbodydevices work in unison to allow movement of the vertebrae coupled to thedynamic interbody devices.

In some embodiments, a first dynamic interbody device is placed in aprepared disc space between vertebrae. A second dynamic interbody deviceis also placed in the disc space between the vertebrae. A connector maybe coupled to the first dynamic interbody device and the second dynamicinterbody device. The connector may link the first dynamic interbodydevice to the second dynamic interbody device and provide stabilizationto the dynamic interbody devices. The connector may inhibit migration ofthe dynamic interbody devices. The connector may ensure that the dynamicinterbody devices work in unison to allow movement of the vertebraecoupled to the dynamic interbody devices. In some embodiments, theconnector may slide into the dynamic interbody devices. Detents,adhesive, setscrews or other fastening systems may inhibits separationof the connector from the dynamic interbody devices.

Bridge 70 may include member, 72 and connector 74. In some embodiments,a length of the member is adjustable. A first portion of the member mayslide relative to a second portion of the member. A setscrew or otherfastening system may set the position of the first portion of the memberrelative to the second portion of the member when the desired length ofthe bridge is set. Connector 74 may couple the dynamic interbody deviceto a posterior stabilization system. Connector 74 may include slot 76. Abone fastener of the posterior stabilization system may be positioned inslot 76 to secure the bridge to a vertebra and to the dynamic posteriorstabilization system. In some embodiments, the connector may be a plateor other structure with an opening (e.g., a ring). A shaft of a bonefastener of a dynamic posterior stabilization system may be positionedthrough the opening to secure the bridge to a vertebra and to thedynamic posterior stabilization system.

In some embodiments, the bridge may be a separate component from thefirst member. FIG. 4 depicts an embodiment of separate component bridge70. Connector 74 of bridge 70 may be coupled to the dynamic posteriorstabilization system. End 78 of bridge 70 may contact the dynamicinterbody device during use to couple the bridge to the dynamicposterior stabilization system and inhibit posterior migration and/orbackout of the dynamic interbody device from the disc space.

The connector of a separate component bridge or the connector of abridge that is coupled to a dynamic interbody device may include anangled surface. For example, bridge 70 may include angled surface 80.Angled surface 80 may facilitate alignment of the center of a curvedelongated member of the dynamic posterior stabilization system with atleast one rotation center of the dynamic interbody device (e.g., therotation centers that control flexion/extension and lateral bending ofthe dynamic interbody device) so that the dynamic posteriorstabilization system works in conjunction with the dynamic interbodydevice to allow for motion of the vertebra coupled to the dynamicinterbody device.

In some embodiments where bridge 70 is a separate component, the dynamicinterbody device includes an opening that couples to an inserter. Theinserter may couple to the opening of the dynamic interbody device by adetent, threading and/or other reversible coupling system.

The bridge may couple the dynamic interbody device to the dynamicposterior stabilization system. In some embodiments, the bridge may becoupled to the second bone fastener of the dynamic posteriorstabilization system. The second bone fastener may be secured to themore caudal of the vertebrae being stabilized. A portion of the bridgemay be positioned near the end plate of the more caudal vertebra. Theposition of the bridge may inhibit contact of the bridge with neuralstructures (e.g., spinal ganglion) exiting the vertebrae.

FIG. 5 depicts an embodiment of second member 58. Second member 58 mayinclude ledges 82, first pin 84, first arcuate surface 86, second pins88 (one on each side of the second member), convex surface 90, and upperanterior surface 92. In some embodiments, the second member includes aslot instead of first pin 84. In some embodiments, the second member mayincludes recesses that accommodate pins of the third member to couplethe third member to the second member and allow for flexion/extension ofvertebrae coupled to the dynamic interbody device. The recesses may takethe place of second pins 88.

Ledges 82 may interact with the arms of the first member to inhibitseparation of the first member from second member 58. First pin 84 maybe positioned in the slot of the first member to allow for lateralbending and/or axial rotation of the vertebra coupled to the thirdmember relative to the vertebra coupled to the first member. Firstarcuate surface 86 may have a curvature that complements the curvatureof the arcuate surface of the first member.

Second pin 88 may couple second member 58 to the third member. Curvedsurface 90 may interact with a curved surface of the third member toallow for flexion/extension of the vertebra coupled to the third memberrelative to the vertebra coupled to the first member. In someembodiments, curved surface 90 is convex and the curved surface of thethird member is concave. In some embodiments, the curved surface of thesecond member is concave and the curved surface of the third member isconvex.

The radius of curved surface 90 and the radius of the curved surface ofthe third member may be small so that translational movement of thevertebra coupled to the third member relative to the vertebra coupled tothe first member is kept within a proper range during flexion orextension of the vertebrae. In some embodiments, the radial center ofcurved surface 90, and the corresponding radial center of the curvedsurface of the third member, may be located towards posterior end 94 ofsecond member 58 to limit the amount of posterior translation duringextension.

In some embodiments, upper anterior surface 92 is a contact surface. Alower anterior surface of the third member may contact upper anteriorsurface 92 when the dynamic interbody device is at maximum flexion.

FIG. 6 depicts an embodiment of third member 60. FIG. 7 depicts across-sectional view of an embodiment of third member 60. Third member60 may include outer surface 96, lead surface 98, angled lower posteriorsurface 100, angled lower anterior surface 102, slots 104, and curvedsurface 106. One slot 104 may be formed on each side of third member 60.At least a portion of outer surface 96 may be sloped to provide adesired amount of lordosis between the vertebrae coupled to the firstmember and third member 60. Curved surface 106 may be complementary tothe curved surface of the second member to allow for flexion and/orextension of the vertebra coupled to the first member relative to thevertebra coupled to the third member.

During insertion of the dynamic interbody device in a disc space, thevertebrae may be distracted so that the disc space has a height that isless than the height of the dynamic interbody device. Lead surface 98may contact one of the vertebrae and provide force against the vertebrathat distracts the vertebrae to allow for insertion of the dynamicinterbody device.

In some embodiments, angled lower posterior surface 100 and angled loweranterior surface 102 are contact surfaces. In some embodiments, only oneside of the third member includes an angled lower posterior surface andan angled lower anterior surface. In some embodiments, both sides of thethird member include angled lower posterior surfaces and angled loweranterior surfaces. Having two angled lower posterior surfaces and twoangled lower anterior surfaces may allow the third member to be used ina right dynamic interbody device or a left dynamic interbody device,thus eliminating the need for different left and right third members.

Angled posterior surface 100 may contact the arcuate surface of thefirst member when the dynamic interbody device is at maximum extension.The dynamic interbody device may allow for a maximum of about 15° ofextension from the neutral position. Angled posterior surface 100, thegeometry of one or both slots 104, and/or the geometry of the secondmember may be designed so that the dynamic interbody device has asmaller or a larger maximum angle of extension from the neutralposition. In some embodiments, the dynamic interbody device allows for amaximum of about 7° of extension from the neutral position.

Angled lower anterior surface 102 may contact the arcuate surface of thefirst member when the dynamic interbody device is at maximum flexion.The dynamic interbody device may allow for a maximum of about 20° offlexion from the neutral position. Angled lower anterior surface 102,the geometry of one or both slots 104, and/or the geometry of the secondmember may be designed so that the dynamic interbody device has asmaller or a larger maximum angle of flexion from the neutral position.In some embodiments, the dynamic interbody device allows for a maximumof about 7° of flexion from the neutral position. In some embodiments,the maximum amount of flexion allowed by the dynamic interbody device isdifferent from the maximum amount of extension. For example, anembodiment of a dynamic interbody device allows for a maximum of about15° of flexion and a maximum of about 10° of extension.

The second pins of the second member may be positioned in slots 104 tocouple third member 60 to the second member. Slots 104 may accommodaterotational movement and translational movement of third member 60relative to the second member during flexion and extension.

FIG. 8 depicts an embodiment of dynamic interbody devices 50′, 50″. Eachdynamic interbody device 50′, 50″ may include bridge 70, convex member108 and concave member 110. Convex member 108 and concave member 110 maybe coupled to vertebrae. One or more removable members of a dynamicinterbody device may initially hold the position of convex member 108constant relative to concave member 110. After the dynamic interbodydevice is positioned in a disc space between vertebrae, the removablemember or removable members may be removed to allow concave member 110the ability to move relative to convex member 108.

Curved surface 112 of convex member 108 may have the contour of an outersurface of a portion of a sphere. Concave member 110 may have a curvedsurface that is complementary to curved surface 112 of convex member 108to allow for flexion/extension, lateral bending, and axial rotation ofthe vertebra coupled to convex member 108 relative to the vertebracoupled to concave member 110. In an embodiment, convex member 108includes a protrusion that extends into a recess of the concave member110. In an embodiment, convex member 108 includes a recess and concavemember 110 includes a protrusion that extends into the recess. The sizeof the recess may be designed to limit the available range for flexion,extension, lateral bending and/or axial rotation.

Bridge 70 may include elongated portion 72 and connector 74. A sectionof elongated portion 72 may be a keel for the dynamic interbody devicethat is positionable in a channel formed in a vertebra. The channelsformed in the vertebra for the two dynamic interbody devices may beformed to the same depth and the same distance away from a center lineof the vertebra so that the spherical portions of the right dynamicinterbody device is in working relation to the spherical portion of theleft dynamic interbody device.

In some embodiments, a section of elongated portion 72 may be bendable.Bending elongated portion 72 may allow the dynamic interbody device tobe conformed to the patient so that connector 74 can be coupled to adynamic posterior stabilization system.

Connector 74 may include slot 76 and channel 114 between arms 116. Aportion of a bone fastener may be positioned in slot 76 to couple thedynamic interbody device to a bone fastener. Coupling the bone fastenerto the dynamic interbody device may inhibit backout of the dynamicinterbody device from the disc space between the vertebrae. Coupling thebone fastener to the dynamic interbody device may allow for alignment ofthe center of rotation of the dynamic interbody device with the centerof rotation of a curved elongated member of the dynamic posteriorstabilization system so that the dynamic interbody device works inconjunction with the dynamic posterior stabilization system to allow formovement of the vertebrae coupled to the dynamic interbody device.

An elongated member of a posterior stabilization system or dynamicposterior stabilization system may be positioned in channel 114 betweenarms 116. The elongated member may be coupled to connector 74 to inhibitremoval of the elongated member from channel 114. The elongated memberof a dynamic posterior stabilization system may be coupled to connector74 such that translational and/or rotational movement of the elongatedmember relative to arms 116 is not inhibited.

FIG. 9 depicts an embodiment of dynamic posterior stabilization system118. Dynamic posterior stabilization system 118 may include closuremembers 120; first bone fastener 122; second bone fastener 124;elongated member 126; and bias members 128, 130. In some embodiments,first bone fastener 122 is positioned in the more upper of the vertebraeto be stabilized. In other embodiments, first bone fastener ispositioned in the lower of the vertebrae to be stabilized.

When closure member 120 couples elongated member 126 to first bonefastener 122, movement of the elongated member relative to the firstbone fastener may be inhibited. When closure member 120 coupleselongated member 126 to second bone fastener 124, translational and/orrotational movement of the elongated member relative to the second bonefastener may be possible. The ability to have translational movement ofelongated member 126 relative to second bone fastener 124 may allowdynamic posterior stabilization system 118 to accommodate flexion,extension and lateral bending of a first vertebra coupled to the dynamicposterior stabilization system relative to a second vertebra coupled tothe dynamic posterior stabilization system. The ability to haverotational movement of elongated member 126 relative to second bonefastener 124 may allow dynamic posterior stabilization system 118 toaccommodate axial rotation of the first vertebra coupled to the dynamicposterior stabilization system relative to the second vertebra coupledto the dynamic posterior stabilization system.

FIG. 10 depicts an embodiment of closure member 120. Closure member 120may couple the elongated member of the dynamic posterior stabilizationsystem to the first bone fastener or to the second bone fastener.Closure member 120 may include threading 134 or other structure thatsecures the closure member to a collar of the first bone fastener 122 orto a collar of the second bone fastener. Closure member 120 may includetool opening 136. A portion of a driver may be inserted into toolopening 136 to facilitate attaching closure member 120 to the collar ofthe first bone fastener or to the collar of the second bone fastener.

Closure members may be other types of fasteners, including but notlimited to clips and snap on connectors. In some embodiments, theclosure member coupled to the first bone fastener may be different fromthe closure member coupled to the second bone fastener. For example, theclosure member used to secure the elongated member to the first bonescrew may be a closure member as depicted in FIG. 10, while a closuremember used to couple the elongated member to the second bone fastenermay be a clip that allows the elongated member to move relative to thesecond bone fastener.

As shown in FIG. 9, dynamic posterior stabilization system 118 includeselongated member 126. Elongated member 126 may be a rod, bar, plate,combination thereof, or other type of member coupled to first bonefastener 122 and second bone fastener 124. In some embodiments where thedynamic posterior stabilization system is to be used with a dynamicinterbody device, elongated member 126 may be bent so that the elongatedmember has a curvature that facilitates the use of the dynamic posteriorstabilization system in conjunction with the dynamic interbody device.In embodiments where the dynamic posterior stabilization system is notused in conjunction with a dynamic interbody device, the elongatedmember may be straight or curved. Elongated members with appropriatecurvature may be included in the instrument kit for the spinalstabilization procedure.

FIG. 11 depicts an embodiment of bent elongated member 126. In anembodiment, a portion of elongated member 126 near first end 138 issecured to the first bone fastener of the dynamic posteriorstabilization system so that movement of the elongated member relativeto the first bone fastener is inhibited. A portion of elongated member126 near second end 140 may be coupled to the second bone fastener ofthe dynamic posterior stabilization system so that translationalmovement and or rotational movement of the elongated member relative tothe second bone fastener is allowed. In some embodiments, concaveportion 142 of elongated member 126 may be oriented to face thevertebrae coupled to the dynamic posterior stabilization system so thata center of the curve aligns or substantially aligns with the center orcenters of rotation of the dynamic interbody device that allow forflexion/extension and/or lateral bending. The alignment or substantialalignment allows the dynamic posterior stabilization system and thedynamic interbody device to simultaneously accommodate flexion/extensionand/or lateral bending of the vertebrae being stabilized. In someembodiments, a portion of elongated member 126 near second end 140 maybe bent so that the elongated member does not contact or approach avertebra during patient movement.

As shown in FIG. 9, an end of elongated member 126 near second bonefastener 124 may include stop 132. Stop 132 may retain bias member 130on elongated member 126. In some embodiments, the position of the stopmay be adjustable along the length of the elongated member. A fixedposition stop or an adjustable position stop may be used in conjunctionwith bias member 128 instead of using the collar of first bone fastener122 as the stop for bias member 128. In some embodiments, a removablestop may initially maintain bias member 128 in compression. In someembodiments, a removable stop may initially maintain bias member 128 incompression. The removable stops may facilitate coupling elongatedmember 126 to second bone fastener 124. After elongated member 126 iscoupled to second bone fastener 124, the removable stops may be removedso that the bias members can accommodate movement of the elongatedmember relative to the second bone fastener caused by flexion/extensionand/or lateral bending. In some embodiments, an insertion instrument mayhold bias members 128, 130 in compression when elongated member 126 isbeing coupled to first bone fastener 122 and second bone fastener 124.

Bias members 128, 130 may surround or partially surround elongatedmember 126. Bias members 128, 130 may be stacks of elastic washers,elastic tubes, springs, or other systems that provide resistance tocompression. In some embodiments, bias members 128, 130 may be formed ofbiocompatible polymeric material. For example, bias members 128, 130 maybe formed of silicone-urethane co-polymer.

Bias members 128, 130 may transmit little or no force to second bonefastener 124 when dynamic posterior stabilization system 118 is in aneutral position. If second bone fastener 124 is coupled to the morecaudal vertebra of the vertebrae to be stabilized, compression of biasmember 128 may accommodate translational movement of elongated member126 caused by extension and/or lateral bending of the vertebrae coupledto dynamic posterior stabilization system 118. If second bone fastener124 is coupled to the more caudal vertebra of the vertebrae to bestabilized, compression of bias member 130 may accommodate translationalmovement of elongated member 126 caused by flexion and/or lateralbending of the vertebrae coupled to dynamic posterior stabilizationsystem 118.

Bias member 128 may accommodate up to about 3 mm of travel of secondbone fastener 124 towards first bone fastener 122. Bias member 130 mayaccommodate up to about 2 mm of travel of second bone fastener 124 awayfrom first bone fastener 122.

In some embodiments, bias member 128 and bias member 130 are the same.For example, bias members 128, 130 may be stacks of washers. In someembodiments, bias member 128 is different than bias member 130. Forexample, bias member 128 is a spring, and bias member 130 is an elastictube.

Bias members 128, 130 may allow dynamic posterior stabilization system118 to provide stability while still allowing for anatomical motion anddynamic resistance that mimics normal segmental stiffness of the spine.Knowledge of the elastic properties (e.g., the amount of compression perdegree of rotation) of the material chosen for bias members 128, 130allows the length of the bias members placed on the elongated member tobe selected so that the dynamic posterior stabilization system providesa desired amount of resistance. FIG. 12 depicts a plot of the appliedmoment versus the amount of rotation for an intact (normal) functionalspinal unit (plot 144), for an unconstrained functional spinal unit(plot 146), and for a functional spinal unit with a dynamic posteriorstabilization system (plot 148). The slope of the curves at each pointrepresents spinal stiffness. The neutral zone is the low stiffnessregion of the range of motion. The dynamic posterior stabilizationsystem may allow for stabilization of the spine while providingsubstantially unconstrained motion within the neutral zone andincreasing resistance to rotation within the elastic zone. The stiffnessof vertebrae supported by the dynamic posterior stabilization system mayclosely mimic the stiffness of a normal functional spinal unit. Thebehavior of the dynamic posterior stabilization system may closely mimicthe normal kinematics of the functional spinal unit.

FIG. 13 depicts the components of an embodiment of first bone fastener122. First bone fastener 122 may include fastener 150, collar 152, andsaddle 154. Fastener 150 may include shaft 156 and head 158. Shaft 156may secure first bone fastener 122 to bone (e.g. a vertebra). Shaft 156may include threading 160 that secures the shaft to the bone.

A portion of outer surface 162 of head 158 may have a spherical contourcomplementary to a portion of spherically contoured inner surface 172 ofcollar 152. The shape of outer surface 162 and inner surface 172 ofcollar 152 may allow for polyaxial positioning of the collar relative tofastener 150. Inner surface 164 of head 158 may be sphericallycontoured. The spherical contour of inner surface 164 may allow saddle154 to be positioned in fastener 150 at a desired angle to accommodatethe position of collar 152 relative to the fastener.

Collar 152 may include arms 166 and lower body 168. A portion of theelongated member may be positioned in the slot between arms 166. Aportion of the inner surfaces of arms 166 may include threading 170 thatis complementary to threading of the closure member used to secure theelongated member to first bone fastener 122. Portion 172 of the innersurface of lower body 168 may have a spherically contoured section thatcomplements the spherical contour of outer surface 162 of fastener head158 to allow for polyaxial positioning of collar 152 relative tofastener 150.

Head 158 of fastener 150 may be positioned in collar 152 to form afastener and collar combination. FIG. 14 depicts a top view of fastenerand collar combination 174. When head 158 is positioned in collar 152,separation of the fastener from the collar may be difficult. Severalfastener and collar combinations 174 may be provided in an instrumentkit for a dynamic spinal stabilization procedure. The instrument kit mayinclude several combinations 174 with fasteners 150 of varying lengths.For example, the kit may include fastener and collar combinations withfastener having lengths from about 30 mm to about 75 mm in 5 mmincrements. In some embodiments, collar 152 of each combination 174 isstamped, printed or etched with the length of fastener 150. Fasteners150 and/or collars 152 of combinations 174 in the instrument kit may becolor coded to indicate the length of the fasteners. For example, thecollars of all combinations in the instrument kit with fasteners 150that are about 30 mm in length have an orange color, the collars of allcombinations in the instrument kit with fasteners that are about 35 mmin length have a yellow color, and the collars of all combinations withfasteners that are about 40 mm in length have a green color. Additionalcolors may be used for additional sizes.

Fastener 150 may include tool opening 176. Tool opening 176 maycomplement a head of a driver. The driver may be used to insert fastener150 into bone. The driver may be included in the instrument kit for thespinal stabilization procedure. In some embodiments, arms 166 mayinclude flats, recesses or openings that engage insertion tools orguides.

Referring to FIG. 13, saddle 154 may have post 178 and support 180.Saddle 154 may be positioned in fastener 150 after the fastener andcollar combination has been inserted into a vertebra. Post 178 may bepositioned in fastener 150. Post 178 may be angled within head 158 offastener 150 so that saddle 154 can accommodate polyaxial positioning ofcollar 152 relative to the fastener. In some embodiments, a retainingring inhibits separation of saddle 154 from fastener 150.

Support 180 may include groove 182. A portion of the elongated member ofthe dynamic posterior stabilization system may be positioned in groove182. In some embodiments, saddle 154 and/or collar 152 are shaped sothat groove 182 aligns with the slot formed between arms 166 of collar152 when the saddle is placed in the collar.

A portion of the elongated member may, be positioned in groove 182. Theclosure member for first bone fastener 122 may be threaded on collar 152and tightened against elongated member 126. In some embodiments, theclosure member may include one or more points or edges that bite intothe elongated member when the closure member is tightened against theelongated member. When the closure member is tightened against theelongated member, the position of collar 152 relative to fastener 150may become fixed, and movement of the elongated member relative to firstbone fastener may be inhibited.

FIG. 15 depicts an embodiment of second bone fastener 124. Second bonefastener 124 may include fastener 150, collar 152, saddle 154, and cover184. Fastener 150, collar 152, and saddle 154 of second bone fastener124 may be substantially the same as the fastener, collar and saddle ofthe first bone fastener. Cover 184 may include groove 186.

Saddle 154 may be positioned in collar 152 after the fastener and collarcombination are inserted into a vertebra. A portion of the elongatedmember may be positioned in groove 182 of saddle 154. Cover 184 may bepositioned on top of the elongated member. The radius of groove 186 maybe larger than the radius of the portion of the elongated memberpositioned in the groove. The closure member for second bone fastener124 may be threaded on collar 152 and tightened against cover 184. Insome embodiments, the closure member may include one or more points oredges that bite into cover 184 when the closure member is tightenedagainst the cover. The position of collar 152 relative to fastener 150may become fixed when the closure member is tightened against cover 184.Having the radius of groove 186 larger than the radius of the portion ofthe elongated member positioned in the groove may allow translationalmovement and/or rotational movement of the elongated member relative tosecond bone fastener 124 when the closure member couples the elongatedmember to the second bone fastener.

When a closure member secures the elongated member between saddle 154and cover 184, significant change in height of the elongated memberrelative to second bone fastener 124 may be inhibited. Inhibiting heightchange of the elongated member relative to second bone fastener mayallow the dynamic posterior stabilization system to share a portion ofthe shear load applied to a dynamic interbody device or intervertebraldisc between the vertebrae being stabilized.

In some dynamic posterior stabilization system embodiments, theelongated member may be positioned lateral to the first bone fastenerand/or the second bone fastener. FIG. 16 depicts a top viewrepresentation of an embodiment of dynamic posterior stabilizationsystem 118 where elongated member 126 is positioned lateral to secondbone fastener 124. A closure member may secure elongated member 126 tofirst bone fastener 122 so that movement of the elongated memberrelative to the first bone fastener is inhibited.

Second bone fastener 124 may include member 188. A portion of member mayslide over or into a portion of collar 152 of second bone fastener 124.The connection between the collar and member may inhibit rotation ofmember 188 relative to collar 152. A closure member may secure member188 to collar 152 and second bone fastener 124. When the closure membersecures member 188 to collar 152 movement of second bone fastener 124relative to elongated member 126 is allowed. Second bone fastener 124may be able to move axially relative to elongated member 126 toaccommodate flexion/extension and/or lateral bending of vertebraecoupled to the dynamic posterior stabilization system. Second bonefastener 124 may also be able to rotate relative to elongated member 126to accommodate axial rotation of vertebrae coupled to the dynamicposterior stabilization system.

FIG. 17 depicts a front view of a portion of second bone fastener 124 ofFIG. 16 with member 188 coupled to collar 152 of the second bonefastener. Member 188 may include slot 190. A portion of elongated member126 may pass through slot 190. Slot 190 and/or the portion of elongatedmember 126 that can pass through slot may have cross sectional shapesthat accommodate rotation of second bone fastener 124 relative to theelongated member so that the dynamic posterior stabilization system isable to accommodate axial rotation of vertebrae being stabilized. Secondbone fastener 124 may also be able to move axially along elongatedmember 126 so that the dynamic posterior stabilization system canaccommodate flexion/extension and/or lateral bending of vertebrae beingstabilized.

Placement of the elongated member adjacent to the second bone fastenermay allow for construction of a multi-level dynamic posteriorstabilization system. FIG. 18 depicts a multi-level dynamic posteriorstabilization system that includes dynamic posterior stabilizationsystem 118′ and dynamic posterior stabilization system 118″. Elongatedmember 126″ of dynamic posterior stabilization system 118″ may bepositioned in and secured to the collar of second bone fastener 124′ ofdynamic posterior stabilization system 118′. A mirror image dynamicposterior stabilization system construction may be installed on thecontralateral side of the spine.

During lateral bending of a first vertebra relative to a secondvertebra, the geometry of the facet joints may cause some axial rotationto occur. In some embodiments, the dynamic posterior stabilizationsystem may be designed to cause some axial rotation during lateralbending. FIG. 19 depicts a top view representation of dynamic posteriorstabilization system 118 that may introduce some axial rotation whenlateral bending occurs. All of elongated member 126 or a portion of theelongated member that passes through member 188 may have a non-circularcross section. The passage of the opening for the elongated memberthrough member 188 may be at an angle. In some embodiments, theorientation of the slot for elongated member 126 at the entrance intomember 188 may be different than the orientation of the slot for theelongated member at the exit of the member. Interaction of elongatedmember 126 with member 188 may allow for some automatic rotation ofsecond bone fastener 124 relative to the elongated member when thesecond bone fastener moves laterally relative to first bone fastener122.

In some dynamic posterior stabilization system embodiments, theelongated member may be at a substantially fixed height relative to thesecond bone fastener. In some dynamic posterior stabilization systemembodiments, the elongated member may angulate so that the height of theelongated member relative to the second bone fastener is variable.Allowing the height of the elongated member relative to the second bonefastener to vary may allow for the use of a straight elongated memberwith a dynamic interbody device.

FIG. 20 depicts a top view representation of an embodiment of dynamicposterior stabilization system 118. Dynamic posterior stabilizationsystem 118 may include first bone fastener 122, second bone fastener124, elongated member 126, and bias members 128, 130. Elongated member126 may include threaded portion 192. Second bone fastener 124 mayinclude member 188. Member 188 may allow elongated member 126 to bepositioned lateral to the fastener of second bone fastener 124. Lateralplacement of the elongated member may allow for the establishment ofmulti-level stabilization systems. The elongated member of a seconddynamic posterior stabilization system may couple to the collar of thesecond bone fastener of the first dynamic posterior stabilizationsystem. In some embodiments, the member may position the elongatedmember through the collar of the second bone fastener.

FIG. 21 depicts a front view representation of a portion of second bonefastener 124. Member 188 may include slot. Slot 190 may allow for changein vertical position of elongated member 126 relative to second bonefastener 124. Change in vertical position of elongated member 126relative to second bone fastener 124, along with the compression of onethe bias members, may allow the dynamic posterior stabilization systemto accommodate flexion or extension of vertebrae coupled to the dynamicposterior stabilization system.

The portion of elongated member 126 positioned in slot 190 may have oneor more flats. For example, elongated member 126 may have a hexagonalportion. The flats may interact with member 188 to inhibit rotation ofelongated member 126 relative to second bone fastener 124 while stillallowing for changes in vertical position of the elongated memberrelative to the second bone fastener. Elongated member 126 may be ableto rotate relative to the first bone fastener so that the dynamicposterior stabilization system is able to accommodate axial rotation ofa first vertebra coupled to the first bone fastener relative to a secondvertebra coupled to the second bone fastener.

FIG. 22 depicts a side view representation of a portion of dynamicposterior stabilization system 118 with a portion of first bone fastener122 depicted in cutaway to emphasize the interior of the first bonefastener. Ball 194 may be threaded on threaded portion 192 of elongatedmember 126. Ball 194 may be positioned in collar 152 of first bonefastener 122. Ball 194 may allow elongated member 126 to be pivotablycoupled to first bone fastener 122. Closure member 196 for first bonefastener 122 may include a spherically shaped portion that complements aportion of the outer surface of ball 194. In some embodiments, thecollar of the second bone fastener may accept a closure member that isidentical to closure member 196 for first bone fastener 122 to avoid theneed for different types of closure members for the first bone fastenerand the second bone fastener.

In some embodiments, one or more lock rings may be placed on thethreaded end of the elongated member. After the position of the ball isadjusted so that the elongated member will fit in the first bonefastener and the second bone fastener, one or more lock rings may bepositioned against the ball to inhibit rotation of the ball relative tothe elongated member. In some embodiments, an adhesive may be used toinhibit change in position of the ball relative to the elongated memberafter the position of the ball is set. Other systems may also be used toinhibit change in position of the ball relative to the elongated memberafter the position of the ball is set. In some embodiments, a portion ofthe end of the elongated member may be removed after the position of theball is set so that there is little or no extension of the end of theelongated member beyond the collar of the first bone fastener when thedynamic posterior stabilization system is assembled.

In some embodiments, the ball may be at a fixed position on theelongated member. The length of the elongated member may be adjustableto allow the elongated member to be positioned in the first bonefastener and the second bone fastener. In an embodiment, a first portionof the elongated member may move relative to a second portion of theelongated member. A setscrew or other fastener may fix the position ofthe first portion relative to the second portion. Having a fixedposition of the ball allows little or no extension of the end of theelongated member beyond the collar of the first bone fastener.

When closure member 196 is secured to collar 152 of first bone fastener122, the closure member and the collar may allow rotation of ball 194relative to the first bone fastener. Rotation of ball 194 allows forrotation and/or angulation of elongated member 126 relative to firstbone fastener 122.

Closure member 196, collar 152 and ball 194 may allow for angulation ofelongated member 126 relative to first bone fastener 122. The angularmovement of elongated member 126, along with compression of bias member128 or bias member 130, allows dynamic posterior stabilization system118 to accommodate flexion/extension and/or lateral bending of thevertebrae coupled to the dynamic posterior stabilization system.

Elongated member assemblies may be provided in the instrument kit forthe spinal stabilization procedure. The elongated member assemblies mayinclude elongated member 126; ball 194 threaded on the elongated member;member 188; bias members 128, 130; and stops 132. During an installationprocedure, the fastener of the first bone fastener 122 and the fastenerof second bone fastener 124 may be positioned in the vertebrae to bestabilized. Bridge 70 may be positioned between the collar of secondbone fastener 124 and the vertebra to which the second bone fastener isattached. Bridge 70 may be secured to the vertebra by the collar of thesecond bone fastener.

The position of ball 194 on elongated member 126 may be adjusted byrotating the ball relative to the elongated member until the position ofthe ball on the elongated member allows the ball to be positioned incollar 152 of first bone fastener 122 when member 188 is positioned inthe collar of second bone fastener 124. Member 188 may be coupled to thecollar of the second bone fastener and ball 194 may be positioned incollar 152 of first bone fastener 122. Closure member 196 may be used tosecure member 188 to second bone fastener 124. Closure member 196 may beused to couple ball 194 to collar 152 of first bone fastener 122.

In some dynamic posterior stabilization system embodiments, the passagethrough the second bone fastener for the elongated member may inhibitrotation of the elongated member and may also inhibit angulation of theelongated member relative to the second bone fastener. The second bonefastener may be configured to move axially relative to the elongatedmember when the second bone fastener is coupled to a vertebra. The firstbone fastener may inhibit axial movement of the elongated memberrelative to the first bone fastener, but the first bone fastener mayallow for rotation of the elongated member relative to the first bonefastener. At least a portion of the elongated member may be curved sothat the assembled dynamic posterior stabilization system allows forflexion/extension and/or lateral bending of vertebrae coupled to thedynamic posterior stabilization system. The ability of the elongatedmember to rotate relative to the first bone fastener but not the secondbone fastener may allow for accommodation of axial rotation movement ofvertebrae coupled to the dynamic posterior stabilization system.

FIG. 23 depicts an alternate embodiment of a dynamic posteriorstabilization system that allows elongated member to angulate so thatthe height of the elongated member relative to the second bone fasteneris variable. Dynamic posterior stabilization system 118 may includefirst bone fastener 122, second bone fastener 124, elongated member 126,and bias members 128, 130. Elongated member may be coupled to collar 198of first bone fastener 122 so that rotation of the elongated memberrelative to the first bone fastener about a central axis of theelongated member is inhibited. When elongated member 126 is positionedin collar 198, the elongated member may angulate so that a height of theelongated member relative to second bone fastener 124 is variable.

FIG. 24 depicts a perspective view of an embodiment of elongated member126. Elongated member may include end portion 200. End portion 200 mayfit in a keyway in the collar of the first bone fastener to inhibitremoval of the elongated member from the collar. When end portion 200 ispositioned in the keyway, rotation of the rotation of elongated member126 about the longitudinal axis of the elongated member is inhibited,but the elongated member may be angulated relative to the first bonefastener. FIG. 25 depicts elongated member 126 after insertion intocollar 198 of first bone fastener 122. After insertion, elongated membermay be rotated about the longitudinal axis of the elongated member toseat end portion 200 in the keyway of collar 198.

FIG. 23 depicts dynamic posterior stabilization system after elongatedmember 126 is angulated downward to position a portion of the elongatedmember in collar 202 of second bone fastener 124. When the portion ofelongated member 126 is positioned in collar 202 of second bone fastener124, stop 204 may be coupled to the collar. Stop 204 may inhibit removalof elongated member from collar 202. Bias member 128 may be positionedagainst collar 202, and stop 132′ may be used to fix the position of thebias member. Bias member 130 may be positioned on elongated member 126and stop 132″ may be used to inhibit removal of the bias member from theelongated member.

FIG. 26 depicts a representation of dynamic interbody device 50 andposterior stabilization system 118 positioned between vertebrae 52, 54.Bridge 70 of dynamic interbody device 50 may be coupled to second bonefastener 124 of dynamic posterior stabilization system 1118. Couplingdynamic interbody device 50 to dynamic posterior stabilization system118 may inhibit undesired migration of the dynamic interbody devicerelative to vertebrae 52, 54 while still allowing for flexion,extension, lateral bending, and/or axial rotation of the vertebrae.

When closure member 120 is tightened in collar 152 of second bonefastener 124, a bottom surface of the collar may align and be tightenedagainst angled surface 80 of bridge 70. Tightening closure member 120may fix the position of bridge 70. When closure member 120 is tightenedso that the bottom of collar 152 is positioned against angled surface80, the center of curvature of elongated member 126 may align orsubstantially align with the center or centers of curvature of dynamicinterbody device 50 that allow for flexion/extension and/or lateralbending. Aligning or substantially aligning the center of curvature ofelongated member 126 with the center or centers of curvature of dynamicinterbody device 50 allows the elongated member to move relative tosecond bone fastener 124 during flexion/extension and/or lateral bendingso that dynamic posterior stabilization system 118 works in conjunctionwith the dynamic interbody device.

Dynamic posterior stabilization system 118 may share a portion of theload applied to the vertebrae 52, 54 while providing guidance andresistance to flexion/extension and/or lateral bending that is, or isapproximate to, the resistance provided by a normal functional spinalunit. Allowing for movement of the dynamic interbody device and formovement of the dynamic posterior stabilization system may inhibitdeterioration of adjacent functional spinal units.

In some embodiments, first bone fastener 122 of dynamic posteriorstabilization system is placed in the more cephalad of the vertebrae tobe stabilized. Bridge 70 may couple dynamic interbody device 50 todynamic posterior stabilization system 118. Bridge may be coupled todynamic posterior stabilization system 118 at or near to second bonefastener 124. Coupling bridge 70 to dynamic posterior stabilizationsystem 118 at or near to second bone fastener 124 may inhibit oreliminate contact of the bridge with nerves extending from between thevertebrae.

In some embodiments, a first dynamic posterior stabilization systemcoupled to vertebrae may be unconnected to a second dynamic posteriorstabilization system on a contralateral side of the vertebrae. In someembodiments, one or more transverse connectors may connect dynamicposterior stabilization systems placed on contralateral sides ofvertebrae. FIG. 27 depicts a schematic representation of transverseconnector 206 coupled to dynamic posterior stabilization systems 118′,118″. Transverse connector 206 may be coupled to the collars of secondbone fasteners 124′, 124″. Transverse connector 206 may include firstarm 208, second arm 210, and joint 212. To attach transverse connector206, a fastener of joint 212 may be loosened. First arm 208 may bepositioned in the collar of second bone fastener 124′. Second arm 210may be positioned in the collar of second bone fastener 124″. Closuremember 120′ may secure member 188′ and first arm 208 to second bonefastener 124′. Closure member 120″ may secure member 188″ and second arm210 to second bone fastener 124″. The fastener of joint 212 may betightened. Transverse connector may join dynamic posterior stabilizationsystem 118′ to dynamic posterior stabilization system 118″ and increasethe stiffness of the stabilization system. Attaching transverseconnector 206 to the collars of second bone fasteners 124′, 124″ doesnot inhibit movement of elongated members 126′, 126″ relative to firstbone fasteners 122′, 122″ and/or the second bone fasteners,

In some embodiments, a single dynamic interbody device may be positionedin a disc space between vertebrae. The dynamic interbody device may bepositioned using an anterior, posterior, anterio-lateral, or otherapproach. A bridge may couple the dynamic interbody device to a dynamicposterior stabilization system. In some embodiments, a separatecomponent bridge is coupled to the dynamic posterior stabilizationsystem to inhibit posterior migration of the dynamic interbody device.

In some embodiments, a posterior approach may be used to install astabilization system for a patient. The stabilization system may replaceone or more parts of a functional spinal unit of the patient. Thestabilization system may include one or more dynamic interbody devices,and one or more dynamic posterior stabilization systems.

During a posterior insertion procedure of a spinal stabilization system,a first dynamic interbody device may be installed on a first side of thepatient, and then a second dynamic interbody device may be installed ona second side (contralateral side) of the patient. The dynamic interbodydevices may be bimodal devices. A facet joint between the pair ofvertebrae to be stabilized may be removed on the first side to provideaccess to the intervertebral disc between the vertebrae. Tissue may beretracted to provide access to the intervertebral disc between thevertebrae. A discectomy may be performed to remove all or a portion ofthe intervertebral disc. A channel may be formed in one or both of thevertebrae for the dynamic interbody device or for a keel of the dynamicinterbody device. The dynamic interbody device may be installed in theformed space between the vertebrae.

In some embodiments, a bone fastener may be secured to each of thevertebrae to be stabilized. The bone fasteners may be used duringinsertion of the dynamic interbody device to provide distraction of thevertebrae. The bone fasteners may be components of a dynamic posteriorstabilization system. In some embodiments, a bridge coupled to thedynamic interbody device may be coupled to one of the bone fastenerssecured to the vertebrae.

After the dynamic interbody device on the first side is inserted betweenthe vertebrae, the dynamic posterior stabilization system may be formed.After insertion of the bone fasteners in the vertebrae, the elongatedmember and bias member may be coupled to the bone fasteners.

A second dynamic interbody device may be installed on the contralateralside of the patient. In some embodiments, a transverse connector may becouple the dynamic posterior stabilization system on the first side tothe dynamic posterior stabilization system on the second side.

During some spinal stabilization procedures, posterior elements of thevertebrae to be stabilized may be removed. Pins may be threaded in thevertebrae. The pins may be inserted parallel or inclined away from theendplates of the vertebrae to be stabilized. A discectomy may beperformed to remove the intervertebral disc. The pins may be used toinhibit compression of the disc space between the vertebrae. FIG. 28depicts pins 214 positioned in vertebrae 52, 54 on a first side of thepatient. Pins may also be positioned in vertebrae 52, 54 on the secondside of the patient.

Pins 214 may be used to distract the disc space between vertebrae 52,54. In some embodiments, a distraction plug may be inserted in the discspace of the second side to hold the disc space open. A guide of a keelcutter may be placed over a pin. A head of the keel cutter may beimpacted to form a channel in a surface of one of the vertebra. FIG. 29depicts distraction plug 216 positioned in the disc space betweenvertebrae 52, 54. Guide 218 of keel cutter 220 is positioned over pin214, and the keel cutter has been used to form a channel for a dynamicinterbody implant in vertebra 54. After the channel has been formed,keel cutter may be removed from pin 214. The endplates of vertebrae 52,54 may be prepared for the dynamic interbody implant by removing anyosteophytes and/or tissue. A distraction plug 216 may be inserted in thefirst side, and distraction plug 216 may be removed from the secondside. The keel cutter may be placed over the appropriate pin on thesecond side. The keel cutter may be used to form a channel in thevertebra on the second side. The vertebrae on the second side may beprepared for receiving a dynamic interbody device. After the first sideand second side are prepared, the distraction plug may be removed. Theheight of the disc space may be maintained by force applied to pins 214.

Trial implants may be used to determine the heights of the dynamicinterbody devices to be inserted into the prepared disc space.Appropriate dynamic interbody devices may be attached to inserters. Thedynamic interbody devices may be inserted into the prepared disc space.The dynamic interbody devices may be inserted into the disc space androtated to place keels of the dynamic interbody devices in the channelsformed in vertebra. FIG. 30 depicts a representation of dynamicinterbody devices 50′, 50″ inserted in the disc space. Shafts 222 of theinserters 224 should be parallel to each other and dynamic interbodydevices 50′, 50″ should be inserted to the same depth in the disc space.After insertion, the distraction force is removed and the spine isallowed to return to a neutral position. If necessary, pins 214 may beused to compress the vertebrae towards each other. Inserters 224 may beremoved from the dynamic interbody devices.

Pins 214 may be removed from the vertebrae. Fasteners of a dynamicposterior stabilization system may be inserted into the openings in thevertebra where the pins were located. In some embodiments, a bridge maybe coupled to the second bone fastener of the dynamic posteriorstabilization system. Ball 194 (depicted in FIG. 22) on elongated member126 may be positioned on the elongated member so that member 188 couplesto the second bone fastener when the ball is positioned in the firstbone fastener. When ball is positioned in the first bone fastener andmember 188 is coupled to the second bone fastener, closure members maybe secured to the collars of the first bone fastener and the second bonefastener to complete the dynamic posterior stabilization system. Adynamic posterior stabilization system may be formed on each side of thepatient. FIG. 31 depicts dynamic interbody device 50 and dynamicposterior stabilization system 118 coupled to vertebrae 52, 54.

In some embodiments, a dynamic interbody device may be installed betweena pair of vertebrae using an anterior approach. After insertion of thedynamic interbody device, a dynamic posterior stabilization system canbe attached to the vertebrae. In some embodiments, a bridge is coupledto the dynamic posterior stabilization system. In some embodiments, thebridge is coupled to both the dynamic interbody device and the dynamicposterior stabilization system.

In this patent, certain U.S. patents, and U.S. patent applications havebeen incorporated by reference. The text of such U.S. patents and U.S.patent applications is, however, only incorporated by reference to theextent that no conflict exists between such text and the otherstatements and drawings set forth herein. In the event of such conflict,then any such conflicting text in such incorporated by reference U.S.patents and U.S. patent applications is specifically not incorporated byreference in this patent.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as examples of embodiments. Elements and materials maybe substituted for those illustrated and described herein, parts andprocesses may be reversed, and certain features of the invention may beutilized independently, all as would be apparent to one skilled in theart after having the benefit of this description of the invention.Changes may be made in the elements described herein without departingfrom the spirit and scope of the invention as described in the followingclaims.

1-21. (canceled)
 22. A stabilization system for a human spine,comprising: at least one dynamic interbody device configured to bepositioned in a disc space between a first vertebra and a secondvertebra; and at least one dynamic posterior stabilization systemconfigured to be coupled to the first vertebra and the second vertebra,at least one dynamic posterior stabilization system comprising: a firstbone fastener configured to be coupled to the first vertebra; a secondbone fastener configured to be coupled to the second vertebra; and anelongated member configured to be coupled to the first bone fastener andthe second bone fastener, wherein the elongated member is coupled to thesecond bone fastener such that the second bone fastener can moverelative to the elongated member to accommodate movement of vertebraecoupled to the first bone fastener and the second bone fastener, andwherein at least a portion of the elongated member is curved.
 23. Thestabilization system of claim 22, wherein at least one dynamic interbodydevice includes a center of rotation that accommodates flexion ofvertebra coupled to the dynamic interbody device, and wherein a centerof curvature of the curved portion of the elongated member aligns orsubstantially aligns with the center of rotation of the dynamicinterbody device when the dynamic interbody device and the dynamicposterior stabilization system are coupled to vertebrae.
 24. Thestabilization system of claim 22, further comprising a bridge coupled toat least one dynamic posterior stabilization system.
 25. Thestabilization system of claim 22, further comprising a bridge coupled toat least one dynamic posterior stabilization system and to at least onedynamic interbody device.
 26. The stabilization system of claim 22,further comprising at least one bias member coupled to the elongatedmember, wherein at least one bias member is configured to resistmovement of the second bone fastener relative to the first bone fastenerthat accommodates flexion/extension and/or lateral bending movement ofvertebrae coupled to the dynamic posterior stabilization system.
 27. Thestabilization system of claim 26, wherein the resistance provided by theat least one bias member mimics the resistance to movement provided by anormal functional spinal unit.
 28. The stabilization system of claim 22,wherein at least one dynamic posterior stabilization system comprises amulti-level dynamic posterior stabilization system.
 29. A stabilizationsystem for a human spine, comprising: at least one dynamic interbodydevice configured to be positioned in a disc space between a firstvertebra and a second vertebra; and at least one dynamic posteriorstabilization system configured to be coupled to the first vertebra andthe second vertebra, at least one dynamic posterior stabilization systemcomprising: a first bone fastener configured to be coupled to the firstvertebra; a second bone fastener configured to be coupled to the secondvertebra; and an elongated member configured to be coupled to the firstbone fastener and the second bone fastener when the first bone fastenerand second bone fastener are coupled to the first vertebra and thesecond vertebra, wherein at least a portion of the elongated member iscurved; and wherein longitudinal movement of the first bone fastenerrelative to the elongated member is inhibited, and wherein the secondbone fastener is allowed to move longitudinally along a portion of theelongated member to accommodate flexion of the second vertebra relativeto the first vertebra.
 30. The stabilization system of claim 29, whereinrotation of the elongated member relative to the first bone fastener isinhibited when the elongated member is coupled to the first bonefastener, and wherein rotation of the elongated member relative to thesecond bone fastener is allowed to accommodate axial rotation of thefirst second vertebra relative to the first vertebra.
 31. Thestabilization system of claim 29, wherein rotation of the elongatedmember relative to the second bone fastener is inhibited when theelongated member is coupled to the first bone fastener, and whereinrotation of the elongated member relative to the first bone fastener isallowed to accommodate axial rotation of the first second vertebrarelative to the first vertebra.
 32. The stabilization system of claim29, wherein at least one dynamic interbody device includes a center ofrotation that accommodates flexion of vertebra coupled to the dynamicinterbody device, and wherein a center of curvature of the curvedportion of the elongated member aligns or substantially aligns with thecenter of rotation of the dynamic interbody device when the dynamicinterbody device and the dynamic posterior stabilization system arecoupled to vertebrae.
 33. The stabilization system of claim 29, furthercomprising a bridge coupled to at least one dynamic posteriorstabilization system.
 34. The stabilization system of claim 29, furthercomprising a bridge coupled to at least one dynamic posteriorstabilization system and to at least one dynamic interbody device. 35.The stabilization system of claim 29, further comprising at least onebias member coupled to the elongated member, wherein at least one biasmember is configured to resist movement of the second bone fastenerrelative to the first bone fastener that accommodates flexion/extensionand/or lateral bending movement of vertebrae coupled to the dynamicposterior stabilization system.
 36. The stabilization system of claim35, wherein the resistance provided by the at least one bias membermimics the resistance to movement provided by a normal functional spinalunit.
 37. The stabilization system of claim 29, wherein at least onedynamic posterior stabilization system comprises a multi-level dynamicposterior stabilization system.
 38. A method of stabilizing a portion ofa human spine, comprising: coupling at least one dynamic interbodydevice to a first vertebra and a second vertebra; securing a first bonefastener to the first vertebra; securing a second bone fastener to thesecond vertebra; coupling an elongated member to the first bone fastenerto inhibit movement of the first bone fastener longitudinally withrespect to the elongated member, wherein at least a portion of theelongated member is curved; and coupling the elongated member to thesecond bone fastener to allow longitudinal movement of the elongatedmember with respect to the second bone fastener.
 39. The method of claim38, further comprising: securing a third bone fastener to a thirdvertebra; coupling a second elongated member to the second bone fastenerto inhibit movement of the second bone fastener longitudinally withrespect to the second elongated member; and coupling the elongatedmember to the third bone fastener to allow longitudinal movement of thethird elongated member with respect to the third bone fastener.
 40. Themethod of claim 38, further comprising coupling a bridge to the secondbone fastener.
 41. The method of claim 38, wherein coupling at least onedynamic interbody device to a first vertebra and a second vertebracomprises separating the first vertebra from the second vertebra to forma disc space between the vertebrae, positioning a first dynamicinterbody device in the disc space on the first side of the vertebrae,and positioning a second dynamic interbody device on a contralateralside of the vertebrae in the disc space. 42-121. (canceled)